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WG4 Summary and Future Plans

• The muon trio
• and
• more

B. Lee Roberts Department of Physics Boston
University
roberts_at_bu.edu http//physics.bu.edu/robert
s.html
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The Muon Trio

• Lepton Flavor Violation
• Muon MDM (g-2) chiral changing
• Muon EDM

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MEG
MECO
PRIME
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Today with ee- based theory
All E821 results were obtained with a blind
analysis.
world average
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Electric and Magnetic Dipole Moments
Transformation properties
An EDM implies both P and T are violated. An EDM
at a measureable level would imply non-standard
model CP. The baryon/antibaryon asymmetry in the
universe, needs new sources of CP.
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Present EDM Limits
projected
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General Statements

• We know that n oscillate
• neutral lepton flavor violation
• Expect Charged lepton flavor violation at some
  level
• enhanced if there is new dynamics at the TeV
  scale
• in particular if there is SUSY
• We expect CP in the lepton sector (EDMs as
  well as n oscillations)
• possible connection with cosmology (leptogenesis)

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The Physics Case

• Scenario 1
• LHC finds SUSY
• MEG sees m ? e g
• The trio will have SUSY enhancements
• to understand the nature of the SUSY space we
  need to get all the information possible to
  understand the nature of this new theory

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SUSY predictions of m-A ? e-A
From Barbieri,Hall, Hisano
Rme
MECO single event sensitivity
PRIME single event sensitivity
100 200
300 100 200
300

• ? eg m-A ? e-A Branching
• Ratios are linearly correlated

Complementary measurements (discrimination
between SUSY models)
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Connection with n oscillations
Additional contribution to slepton mixing from
V21, matrix element responsible for solar
neutrino deficit. (J. Hisano N. Nomura, Phys.
Rev. D59 (1999) 116005).
tan(b) 30
tan(b) 0
Largely favoured and confirmed by Kamland
After Kamland
MEG goal
All solar n experiments combined
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SUSY connection between am , Dµ , µ ? e

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aµ sensitivity to SUSY (large tanb)
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SUSY, dark matter, (g-2) DE821
CMSSM
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D E969 Dnow
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D E969 0
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The Physics Case

• Scenario 2
• LHC finds Standard Model Higgs at a reasonable
  mass, nothing else, (g-2) discrepancy could be
  the only indication beyond neutrino mass of New
  Physics
• Then precision measurements come to the
  forefront, since they are sensitive to heavier
  virtual particles.
• µ-e conversion is especially sensitive to other
  new physics besides SUSY

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Sensitivity to Various me Conversion Mechanisms
Supersymmetry
Compositeness
Predictions at 10-15
Second Higgs doublet
Heavy Neutrinos
Heavy Z, Anomalous Z coupling
Leptoquarks
After W. Marciano
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?-N ? e-N vs. m?e g as Probes of LFV

• ?-N ? e-N is more sensitive for essentially all
  processes not mediated by photon
• ?-N ? e-N is more sensitive than is ??e g to
  chirality conserving processes
• ??e g is more sensitive for processes mediated by
  photons
• B(??e ?) ? 300 ? Rme for these processes
• The motivation is sufficiently strong that both
  experiments should be done
• Relative rates for ??e g and ?-N ? e-N would give
  information on underlying mechanism
• A significant rate for ??e g with polarized muons
  could give additional information on mechanism

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The Experiments LFV

• µe conversion and Muonium-anti-Muonium conversion
  
• pulsed beam
• µ? eg and eee
• DC beam

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Near Term Experiments on LFV

• MEG _at_ PSI (under construction, data begins in
  2006)
• 10-13 BR sensitivity
• MECO _at_BNL (funding not certain)
• 10-17 BR sensitivity

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MEG _at_ PSI (10-13 BR sensitivity)
Discovery Potential 4 Events BR 2 X
10-13
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The MECO Apparatus
Straw Tracker
Muon Stopping Target
Muon Beam Stop
Superconducting Transport Solenoid
(2.5 T 2.1 T)
Crystal Calorimeter
Superconducting Detector Solenoid (2.0 T
1.0 T)
Superconducting Production Solenoid (5.0
T 2.5 T)
Collimators
approved but not funded
10-17 BR single event sensitivity
p beam
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Future Experiments on LFV

• PRIME-type experiment
• with FFAG muon storage ring
• few X 10-19
• Such an experiment is perfect for the front end
  of a muon factory

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(No Transcript)
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m e- ? m - e
Muonium production
Full M search
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An improvement of 102 on GMM

• would confront these types of models which
  would also contribute to double b decay. At
  the front end of a n factory with a pulsed beam
  this might be possible.

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Future Muon (g-2) Experiments

• E969 _at_ BNL 0.5 ? 0.20 ppm (scientific approval
  but not funded)
• expected near-term improvement in theory, ? the
  ability to confront the SM by x 2
• The next generation 0.20 ? 0.06 ppm
• substantial RD would be necessary
• new ring or improved present ring?

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Use an E field for vertical focusing
0
spin difference frequency ws - wc
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Muon (g-2) Store m in a storage ring
magnetic field averaged over azumuth in the
storage ring
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E969 Systematic Error Goal

• Field improvements will involve better trolley
  calibrations, better tracking of the field with
  time, temperature stability of room, improvements
  in the hardware
• Precession improvements will involve new scraping
  scheme, lower thresholds, more complete
  digitization periods, better energy calibration

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SM value dominated by hadronic issues

• Lowest order hadronic contribution ( 60 ppm)
• Hadronic light-by-light contribution ( 1 ppm)

The error on these two contributions will
ultimately limit the interpretation of a more
precise muon (g-2) measurement.
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A (g-2) experiment to 0.06 ppm?

• Makes sense if the theory can be improved to 0.1
  ppm, which is hard, but maybe not impossible.
• With the present storage ring, we already have

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Where we came from
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Today with ee- based theory
All E821 results were obtained with a blind
analysis.
world average
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Muon EDM

• Present limit 10-19 e-cm
• Could reach 10-24 to 10-25 at a high intensity
  muon source?

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Spin Precession Frequencies m in B field with
both an MDM and EDM
The motional E - field, ß X B, is much stronger
than laboratory electric fields .
GV/m with no sparks!
The EDM causes the spin to precess out of plane.
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EDM up/down Asymmetry

• avoid the magic ? and use a radial E-field to
  turn off (g-2) precession
• Place detectors above and below the vacuum
  chamber and look for an up/down asymmetry which
  builds up with time

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Up/Down asymmetry vs. time
time
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The EDM ring

• run with both µ and µ-.
• there must be regions of combined EB along
  with separate focusing elements.
• There needs to be a scheme to inject CW and CCW.

Possible Muon EDM Ring Parameters
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A possible lattice
Yuri Orlov
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NP2

• the figure of merit is Nµ times the
  polarization.
• we need
• to reach the 10-24 e-cm level.
• Narrow pulsed beam every 100 ms

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Additional topics

• Muons for condensed matter (m SR)
• Muon catalyzed fusion (m CF)
• Muon lifetime (GF)
• Muon capture (gp)
• . . .

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Depth dependent mSR measurements in near surface
regions
B(z)
Superconductor
l
z
0

• Magnetic field profile B(z) over nm scale
• Characteristic lengths of the sc l, x

? B(z)
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Magnetic Field Profile in YBa2Cu3O7-d

• Direct, absolute measurement of
• magnetic penetration depth

• effective mass
• density of supercarriers

• Direct test of theories (London, BCS)

local response ?? exponential profile
T.J. Jackson, T.M. Riseman, E.M. Forgan, H.
Glückler, T. Prokscha, E. Morenzoni, M. Pleines,
Ch. Niedermayer, G. Schatz, H. Luetkens, and
J. Litterst, Phys. Rev. Lett. 84, 4958 (2000).
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Beams needed

• Pulsed intense muon beams
• energy from surface (28 MeV/c) to 3.1 Gev/c
• A few experiments could used DC beam, but almost
  all can use the pulse structure of a pulse, and
  some ms with no beam

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Beam requirements A few examples
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Plans for next year

• LFV experiments will continue to develop the
  techniques needed for these challenging
  experiments
• Muon EDM collaboration will continue to
  investigate the appropriate ring structure.
• Participate in scoping study for n factory
• At present muon physics is not mentioned in the
  document of 10 June 2005

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Summary

• The questions addressed are at the center of the
  field of particle physics
• There is an important program of muon physics
  which will be possible at the front-end of a n
  factory.
• It makes use of the very intense flux which will
  be available there
• If such a muon facility exists, there will also
  be a program of other very interesting muon
  experiments which is possible.